The present invention relates to a threading apparatus for films which are to be transported through at least one forward stretching machine for films, consisting of driven stationary rolls and driven, raised lift rolls, while the rolls are rotating.
The increased requirements for profitability of film manufacturing lines in which a raw film is oriented in the machine and transverse directions require constantly increasing operating speeds, wider web widths, and absolute cleanliness within the film manufacturing line. Threading the film web through the forward stretching machine is necessary after production is interrupted, when the line is started up, after tears in the web, after a roll change, after changes in production speed, etc. Units to thread films through the forward stretching machine of a film manufacturing machine by means of lines revolving parallel to the front side of the roll are known, as are chains in place of the parallel lines, which transport the threading apparatus through the film forward stretching machine. For narrower film web widths, it is also possible to manually thread the film web while the rolls are standing still.
Previously known mechanical threading units are, in general, suitable only for film web speeds up to 100 m/min. At higher speeds their rate of shutdowns and contamination increases and they become a hazard for the operating personnel. A further disadvantage is the expense of constructing something on the order of rotating lines or chains on both sides of the rolls, which transport the clips which hold the film web as it passes through the film stretching machine.
The Airlift.RTM. system transfers paper webs or sheets between certain sections of a papermaking machine by means of a high flow air current acting in cooperating relationship with a paper guide. See U.S. Pat. Nos. 3,999,696; 4,014,487; and 4,186,860.
The objects of this invention are to improve a film web threading apparatus in such a way that it is suitable for web speeds up to 250 m/min with minimal construction expenditure, operates with as little interruption and contamination as possible, and provides the operators with maximum security against accidents.